Lignes monovariantes de l'isotherme 75 °C du système quaternaire réciproque: H3PO4–K2SO4–H2SO4–K3PO4–H2O

Abstract

The boundary curves and quaternary invariant points of the reciprocal system H3PO4–K2SO4–H2SO4–K3PO4–H2O were investigated at 75 °C and 1 atm by chemical analysis of solutions in equilibria, respectively, with two or three salts. Eleven compounds occur in this system. Only eight of them have crystallization areas inside Janecke's prism; these are K2SO4, K2SO4•KHSO4, K2SO4•7KHSO4•H2O, KHSO4, KH2PO4•KHSO4, KH5(PO4)2, KH2PO4, and a solid solution K8(H2PO4)1+x(HSO4)7−x, 0 ≤ x ≤ 1, of substitution type continuous between the two limiting compositions KH2PO4•7KHSO4 and KH2PO4•3KHSO4. The crystallization fields of 3K2HPO4•KH2PO4•2H2O, K2HPO4, and K3PO4•3H2O are very close to the solubility curves of the ternary system K3PO4–H3PO4–H2O. Results are explained and discussed.